1. Field of Invention
This invention relates to temperature control and power generation of a catalytic converter. More particularly this invention relates to combining the preheating of a catalytic converter and with converting the heat energy of the catalytic converter to electrical energy.
2. Prior Art
In an internal combustion engine vehicle, approximately 80% of the energy consumed leaves the vehicle as waste heat in various forms. For example, heat is emitted from the tail pipe, through the radiator, convected radiated off the engine. Included with the waste heat out the tailpipe are the products of combustion which must meet strict emission standards. To meet these emission standards, the catalytic converter has been a most useful tool.
The allowable emission of pollutants from internal combustion engine vehicles has been dropping and will continue to decrease over the next five years. Some states, California for instance, have requirements that are more stringent than federal standards. Therefore the goal for the automotive industry is to meet these more stringent standards. The acceptable standards have gone from the transitional low emission vehicle (TLEV) of 0. 125/3.4/0.4 g/mile of HC/CO/NOx, instituted in 1994, to the low emission vehicle(LEV) of 0.075/3.4/0.2 g/mile of HC/CO/NOx for 75% of the vehicles sold by 2003. Also by 2003, 15% of the vehicles sold must meet the requirements of the ultra-low emission vehicle (ULEV) of 0.040/1.7/0.2 g/mile of HC/CO/NOx. It is recognized that in a cold start of an internal combustion engine, 70-80% of the hydrocarbon and carbon monoxide pollutants that the vehicle emits occur in the first 100 seconds of operation during the Environmental Protection Agency's Federal Test Procedure (FTP). The FTP is the certification procedure that all vehicles must meet for hydrocarbon, carbon monoxide and nitrous oxide pollutants at the tailpipe. The highest emission of pollutants occurs prior to the catalytic converter reaching light-off temperature, that is, prior to the catalysis monolith becoming active. With early light-off of the catalyst at engine cold start, the internal combustion engine can meet the new pollution requirements.
The objective of reducing the amount of pollutants that exit the tailpipe on cold vehicle start-up must balance between having the exhaust gases that enter the catalytic converter hot enough to expedite the catalyst light-off temperature while at the same time not getting so hot that the catalyst is aged prematurely. Therefore, although insulation of the exhaust system will reduce light-off time, the consequence of reduced catalysis lifetime is an undesirable effect. Exceeding the high temperature limit of the catalyst monolith shortens the life of the catalytic converter.
The standard four-cycle internal combustion engine, whether the mode of operation is a spark-ignition or a diesel engine, operates as an air pump or compressor during part of the cycle. The air pump mode of operation is of interest to this invention during the exhaust stroke, when the engine piston forces the products of combustion out of the cylinder and into the exhaust manifold and exhaust piping. In this portion of the cycle, the engine is operating as an air pump.
There are many prior art concepts aimed at recovering energy from the tailpipe of an internal combustion engine. However, none of the prior art concepts has been applied within a catalytic converter. In the exhaust of an internal combustion engine, there are tremendous temperature differences between a vehicle operating on the highway and a vehicle operating in stop and go traffic on a busy city street. Within a catalytic converter, exothermic reactions take place to convert the pollutants of the combustion process to harmless by-products. The exothermic reactions occur at a relatively high, constant temperature.
During cold start of the internal combustion engine, the catalytic converter is not operating. This could be on a cold winter day when the temperature is -10.degree. C. or on a summer day when the ambient temperature is 30.degree. C. The catalytic converter must be heated to approximately 250.degree. C. before it becomes operable to convert the combustion by-products of the internal combustion engine. Normal operating temperature is in the 400.degree. C. to 800.degree. C. range. For the internal combustion engine to meet the Federal Test Procedure for the new stringent exhaust requirements, the catalyst must come up to temperature as quickly as possible.
What is also needed is a device which would recover some of the waste energy that normally exit the vehicle through the tailpipe is via the conversion to electrical energy in the catalytic converter. This electrical energy would then be available to the electrical system of the vehicle to charge the battery or run any of the electrical components in the vehicle.